No joke - well you may say obviously since this is not a comedy but a horror movie/short ... hopefully you will still allow me to say no pun (or knock for that matter) intended. The director knows how to market his stuff, very active on Instagram and since he was quite successful with another short he gave this another (viral) try.
While you did not have to pay for the km movie, this one had a renting fee, but if you want to encourage and help independent filmmakers you hopefully won't mind. Though Mike happily will accept "hate money" too (I assume). The short which is about 10 minutes long has a simple premise. Though you can speculate about the bad/evil within (deep within I reckon) and way behind ... the door.
Suspension of disbelief is always necessary and this is not an exception of the rule. Once you've accepted the ... let's call it "door opener" (playing of toy), everything else is fair game. Of course the how, why and where as in origin ... well those things are not really answered. But there has to be some mystique to it ... otherwise it might be boring.
There is some minor nudity in this - if you care one way or the other (it actually shouldn't upset or arouse you, but I am not judging either way) and the sound design is really well done ... cinematography is also really good, but the sound is what elevates the whole thing even further.